It is known to control, after the process of filling beverages or other liquids into containers, the fill level of each individual container so as to guarantee that deviations from the target value of the filling content of the container are not excessively high. Typically, containers exhibiting an excessive deviation from the target value of the filling content are rejected from the production stream.
It is e.g. known to measure the fill level optically, by means of high frequency, by means of X-ray or gamma radiation or similar methods. The measuring accuracy is, however, reduced substantially, if the liquid still foams or swashes due to a movement of the container.
Moreover, the fill level can, typically, only be analyzed with a low accuracy of approx. 2 to 3 mm height. In addition, containers, e.g. containers made of plastic, may expand during the filling and conveying procedure, whereby the measurement will become even more inaccurate and e.g. correction factors will have to be used (cf. e.g. DE 10 2006 062 536). Furthermore, optical methods are not suitable for use with containers that are opaque in the area of the upper level of fill, e.g. because they are tin-foiled or labeled in the neck area.
Typically, devices measuring such fill levels must be calibrated individually for each product. In so doing, e.g. the formation of foam of the particular product in the specific plant and/or the temperature and/or the pressure and/or the color of the bottle and/or the product must be taken into consideration. This makes the setting of such devices very expensive, in particular when they are intended to be used with a plurality of products.
It is the object of the invention to solve one or several problems of the prior art.